However, research being undertaken by the Imperial Cancer Research Fund may soon make it possible to match specific cancer drugs to individual cancer patients who are likely to benefit the most, and least likely to suffer
adverse effects.

Writing in the British Medical Journal, Professor Roland Wolf from the Imperial Cancer Research Fund's Pharmacology Unit at Ninewells Hospital, Dundee, and Professor Bob Smith from Imperial College London, say the research may also lead to the development of personalised pills.

These drugs would be designed to fight particular variations of a disease and tailored to an individual's genetic profile.

Professor Wolf and his team study the way drugs are processed by the body and how this varies between individual patients - an area of research known
as pharmacogenetics.

A blood test could give doctors information to tailor make drugs

Pharmacogenetic testing is already being used in some teaching hospitals and academic centres and has been used in Scandinavia for some time.

At the moment, it is most widely used to help tailor drugs and doses for the treatment of psychiatric illness.

Doctors at the Institute of Psychiatry, Kings College, London have used the technique to find a way to predict which schizophrenic patients would be most likely to benefit from treatment with the antipsychotic drug clozapine.

Pharmacogenetics is based on the fact that an individual's response to
certain drugs is determined by their genes.

In previous research cancer experts have identified the genetic difference in a gene, cytochrome P450 CYP2D6, which is very
important in the metabolism of drugs.

Approximately four million people in the UK have a defective form of this gene, which leaves them unable to
break down drugs into an active form or to a form that can be eliminated from the body.

This can either result in a lack of benefit or an adverse
drug reaction - it is therefore pointless to give such drugs to these people.

DNA analysis

Using a small sample, such as blood from a finger prick or cells from a
mouthwash, scientists are able to analyse an individual's DNA.

One day it may be considered unethical not to carry out such tests
routinely to avoid exposing individuals to doses of drugs that could be
ineffective or even harmful to them

British Medical Journal paper

Professor
Wolf said: "By matching the right drug and
dose to the right patient it may be possible to minimise the side effects
while maximising the drug's effectiveness.

"It is already possible for us to
assess patients with psychiatric illnesses and provide them with drugs and
doses that will have a maximum effect while minimising side effects. It is
essential that we can do the same for cancer patients".

In the future, the professors believe that GPs will be able to take a sample from a patient and come up with a drug sensitivity profile for that
person.

They say this could be done by a simple finger prick test, or by taking cells from a mouth wash.

They say: "One day it may be considered unethical not to carry out such tests
routinely to avoid exposing individuals to doses of drugs that could be
ineffective or even harmful to them."

Professor Smith said pharmacogenetics could also help to reduce NHS costs by cutting the need for hospital admission and the length of hospital stays.